Apparatus for making plywood and the like



p 2, 1944. T. w. DIKE ETAL 2,357,880

APPARATUS FOR MAKING PLYWOOD AND THE LIKE Filed Nov. 2, 1959 2Sheets-Sheet 1.

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3] Wu vwtow Theodore ZU. .D/X'e H977 Gab/6e? Sept. 12, 1944. r. w. DIKEETAL 2,357,380

APPARATUS FOR MAKING PLYWOOD AND THE LIKE Filed Nov. 2, 19:59 2Sheets-Sheet 2 Fig. 2.

Fig.5.

Relation between spread cost and duration of assembly time 'gg withMastic glues. C u l v: m! 1| r: n. I 2* H? v H.

:0 g 0 at; i g 2a 83 12545678910 Average Asemb 1y Time Interval :mMmutes.

Glue IMiaser Glue 62 1 1 9.5. Stoc Feeder' 65- 619 2'0 by 21 m vmus w lTl iqad are U Dike 3543 g 'a/ber Patented Sept. 12, 1944 APPARATUS FORMAKING PLYWOOD AND THE LIKE

Theodore Williams Dike and Harry Galber, Seattle, Wash, asslg'nors to I.

F. Laucks, Inc.,

Seattle, Wasln, a corporation of Washington Application November 2,1939, Serial No. soassa 2 Claims.

The present application is a continuation-inpart of our copendingapplication Serial No.

95,460, filed August 11, 1936, now Patent 2,178,566, dated November 7,1939.

Recently, as described in that application (Ser. No. 95,460), we havedeveloped a new type of dispersed glues very useful for hot pressedplywood manufacture and characterized by a very heavy consistency. Theseadhesives are aqueous dispersions preferably of proteinous characterwhich are non-self-flowing and normally occupy a viscosity range betweenabout and 90 No. 18 wire MacMichael, in which range small masses have noflow whatever and large masses flow only slowly under the influence ofgravity. As fully described in our copending application, these .glueshave demonstrated many advantages in hot pressed plywood manufactureincluding remarkable uniformity of adhesion with extremely low spreadcost and great reduction in water injected into the plies as well as inspoilage difliculties such as stain and checking which have formerlyesulted from the tendency of normal fluid glues to migrate deeply 'intothe wood. These nonself-flowing adhesives, owing to their peculiarcharacter, have come to be designated in the industry as mastic glues,and, therefore, for the sake of brevity this descriptive term will beused in the subsequent specification. The above men'- tioned improvedresults in the manufacture of plywood have only been obtained afterextensive research and much experiment to develop a practicalsequence ofsteps for handling material of this peculiar consistency and thesemethods and the required apparatus form the subject of the presentinvention. l

The heavy consistency of mastic glues has pre sented a difficult problemat every stage of the handling beginning with the mixing, continuingthrough the step of transferring the mixed glue to the spreadingapparatus, continuing also in the movement of the glue through thespreader until the material is deposited by the applicator rolls uponthe plies whichare being spread. Our method of handling solves thesedifiiculties, so that, at the moment of spreading and from then on,specialadvantages are obtained which facilitate the operations ofpressing and completing the formation of the glue bond. The presentinvention, therefore, deals with and has for its object the developmentof a complete and satisfactory sequence of steps and arrangement ofapparatus covering the handling of the glue throughout the entireprocess from the original mixing until the glue bond is completed.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described, andparticularly pointed out in the claims, the following descriptionsetting forth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but a few of the variousways in which the principle of the invention may be applied.

We have developed the following sequence of steps in obtaining acommercially practical process of gluing plywood with mastic glues.Preferably, these steps are:

1. Mixing in batches in a powerful mixer which must be of heavyconstruction and adapted to quickly discharge the glue.

2. Discharge from the mixer into a special positive displacement luefeeder capable of supplying theglue to the spreading apparatus underpressure at a controlled rate.

3. Spreading in a modified type of spreading apparatus supplied withspecially reticulated applicator rolls capable of depositing the gluethinly and with extreme'uniformity as a distinct pattern upon thesurfaces of the plies.

4. Assembly of the spread plies with the re-- quired unglued pliesincluding the valuable feature that the uniformity of the glue,distribution is not destroyed or objectionably altered by the handlinginvolved in the assembly operation.

5. Hot pressing with heavy pressure and moderate heat after a carefullycontrolled assembly interval to first transform the pattern depositobtained from the spreading rolls to a thin, uniform all over filmbetween the associated plies and the form a correspondingly uniforminitial glue bond of adequate but limited penetration and at the same.time store in the plies sufficient heat to insure the completion of thebond.

6. Discharge of the plywood from the press as Describing now in detailthe steps in our proc ess and the apparatus required, our experience hastaught the fundamental fact that the inherent character of mastic glueis such that gravity can only be used in moving large masses, and,

that, since the problem of spreading glue upon veneer plies .is forthe-most .part a problem of accurately controlling the distribution ofsmall masses, other means than gravity are necessary for effectiveoperation. This is quite different from the conditions which obtain inthe handling of ordinary fluid glues which due to their mobility canreadily be handled by gravity means, since they will flow satisfactorilythrough pipes and also are able to wet moving surfaces and pick upfairly uniformly on such surfaces and often require only the action ofgravity to remove any undesired excess. With mastic glues theseadvantages are not available and wherever the masses to be moved aresmall, we find it essential to employ pressure greater than gravity and,in some places, we find it is necessary that the displacement of thematerial to its new location be effected by positive means, such as apositive displacement pump. While these restrictions have presented adifficult problem which has only been solved by the development of newmethods and a new sequence of steps in handling the glue, the finalresult is to obtain important advantages and a new efliciency in plywoodmanufacture. These advantages will be apparent in the light of thefollowing description, when considered in connection with theaccompanying drawings, showing, somewhat diagrammatically, preferredmechanism for carrying out the method.

In the drawings:

Figure 1 is a diagrammaticview, partly in side elevation and partly inverticalsection, showing an apparatus, in accordance with the presentinvention. p g

Figure 2 is a vertical section taken substantially on line 2-2 of Figure1.

Figure 3 is a fragmentary rear elevation of. the glue applicator rolls,looking from the right in Figure 1. c

Figure 4 is a fragmentary, enlarged, radial sec;- tion of one of theapplicator rolls. 1

Figure 5 is a graph showing the relation be-, tween the amount of glueapplied and the average assembly time, and

Figure 6 is a diagrammatic plan view of a preferred plant layout.

1. Glue mixing As described in'our copending application, Serial No.95,460,. mastic glues may be made in a wide range of composition, and byusing a variety of constituents, but the essential correct consistencyresults from a substantial restriction of the amount of water usedduring the mixing. When mixing ordinary fluid glues, it is commonpractice to vrestrictthe water during the early stages so as to stir theingredients initially at a heavy consistency to assure great intimacy ofadmixture, but as soon as this condition been obtained, the remainingwateris added and the glue is thinned down to its normal fluid conmasticglue the consistency of, the batch is very heavy at all times, so-thatsatisfactory and emcient mixing involves-the use of a heavilyconstructed machineand the expenditure of asubstantial amount of power.These are the conditions which obtain inmixing bread dough in bakeriesand we find that in practice commercial dough mixers give fairlysatisfactory results. However, for this purpose, dough mixers aregenerally unnecessarily expensive and we prefer to use a simple, butsturdy mixer of the well-known spherical type, such as is shown in theaccompanying drawings. This mixer may comprise a 5 cylindrical containerl0 provided with a hemispherical bottom ll of the same diameter as thecylinder and with two power operated ring stirrers i2, l3 revolved inopposite directions, the outer ring l2 closely fitting the hemisphericalbottom 10 and the inner ring [3 loosely fitting the interior of theouter one,'the rings being driven by horizontal shafts l4, l5,respectively, having pulleys or gears l6, l1 projecting from oppositesides of the mixer. Owing also to the heavy consistency of the glue, weprovide a discharge opening l8 of large diameter, usually about sevenand one-quarter inches in diameter for a spherical mixer having a thirtyinch diameter. With such a discharge opening located near the bottom ofthe mixer and provided with an equally large valve [9, we find thecontents of a batch can be quickly discharged by gravity into theapparatus required for the next step in our process. It is noted thatthis is one of only two instances where we have found it practical torely, at least par-- tially, on gravity as a factor in moving masticglue. Even in this case, however, we find'it necessary to have the mixerrunning when the batch is being discharged, since the action "of thestirring rings is necessary to bring the glue to the discharge openingin sufliciently heavy masses, so that they are able to drop through bygravity. With the apparatus described, however, using a thirty inchmixer with a seven and one-quarter 3 inch discharge opening, we are ableto discharge a glue batch of five hundred and fifty pounds in oneminute. If the above mentioned provision for rapid discharge ofthe batchis not available, difficulty in discharging the completed glue is so 40great that the emptying of the mixer takes longer than the mixing of thebatch.

2. Storing} the glue and supplying the spreader I I In large commercialplywood plants, it is usually necessary to have some kind of .areceiving tank-for the mixed glue to provide a reservoir from which .tosupply the spreader. By this means, the glue mixing is made independentof the glue spreading. With fluid glues this requirement does'notinvolve any difficulty, since any simple overhead tank will act as areservoir and the glue can pass by gravity through a pipe to meet therequirements of the spreader. With mastic glue, such gravity handling isimpossible and it has been-an extremely diflicult problem to make theglue mixing independent of the spreading and atthe same time find somemeans for feeding the heavy non-fluid glue to the spreader at thevarying-rate necessitated by normal flucno tuations in the speed'of thespreading operation.-

At first sight, it would seem that this problem could be readily solvedby providing as the spreader feeder a positive displacement pump of somesort in the bottom of a simple receiving tank.

This method was, in fact, tried a number of times,

but always proved unsatisfactory and the failurewas invariablydue to thesame cause; namely, inability to feed the heavy glue at a uniform ratethrough the intake opening of the pump. In practice, this problem of"feeding the feeder" proved so baffling that an attempt was made toevade it by building a positive displacement pump having an enormouspump chamber capacity, so that the cylinder, which was built in 76 twohalves, could be opened up with the piston retracted and an entire batchof glue .placed in front of the piston-which it was expected could thenbe discharged to the spreader under pressure with satisfactoryuniformity when the pump was closed up and the piston slowly drivenahead by power means. However, this solution gave a great deal oftrouble because a large amount of air was entrapped in front of thefeeder piston which caused a seriously variable discharge and alsoentailed the inconvenience and expense of having a large enoughpiston-chamber to provide a suflicient reservoir between the mixing andspreading operations.

The problem of providing a combined receiving tank and glue feeder wasfinally solved after much costly experiment by providing a cylindricalor cone-shaped open top receiving tank, such as is shown at 25 in theaccompanying drawings. Into this tank, glue is, discharged by gravityfrom the mixer. The capacity of this tank is preferably large enough tohold at least two batches of mixed glue. Just 'below the bottom 26 ofthe tank 25, a powerful but small positive displacement pump 21 isprovided with intake openings 28 penetrating the tank bottom, the pumpbeing located so that the glue moving through these openings isimmediately taken up by the impeller of the pump which is preferably ofthe double spiral type or, alternatively, of the gear type. Power meansare then provided in the receiving tank for both scraping down the sidesand also for continually pressing or squeezing the glue down into theintake openings 28. This scraping and feeding may be accomplished bysecuring a pair of upwardly extending scraper blades 29 to the ends ofarms 30 secured to or integral with,

a hub 3| mounted on a vertically disposed rotatable shaft 32, and bysecuring to those arms, a pair of downwardly and rearwardly inclinedblades 33, positioned to pass over the openings 28 in close proximity tothe floor of the tank and the upper ends of the openings 28. Hence, whenrotational movement is imparted to the shaft 32, the upwardly extendingscraper blades 29 assist in circulating the main body of glue in thetank 25, while the inclined, compression blades or hoes '33 engage theglue adjacent the bottom of the tank and push the same along a circularpath toward the pump intake openings 28. During this movement of theglue by the blades, a strong downward component of force is imparted tothe glue, so that when the blades pass over the openings 28, the glue ispositively forced or squeezed downwardly therethrough, into the pumpchamber.

Rotational force may be impartedto the shaft by any convenient means,for instance, by a gear or pulley 34 secured to the outer end of a shaft35 having, on its inner end, a pinion 36 in mesh with'a similar pinion31 on the shaft 32.

,With this positive method of feeding into the intake of a positivedisplacement pump, pumping action with the heavy non-self-flowingadhesive becomes effectively controllable. It is then possible toregulate the supply to the glue spreader either by by-passing back tothe tank any excess beyond the requirements of the spreader, forinstance, through a conduit 38, or by varying the speed andcorresponding output of the positive displacement. pump. Since theby-pass method eliminates the expense of a variable speed drive, it ispreferred, the supply then being readily controlled by suitable valving,such as valve {3.

Obviously, the foregoing solution of the problem can be effected withvarious types of apparatus, provided provision is made for the essentialfeatures of mechanically hoeing, pressing or squeezing the glue into thepump intake with positive displacement pumping, through a conduit suchas that shown at 40, to the spreader at controllable rate.

3. Spreading mastic glue Modification of the customary double roll gluespreader has also proved necessary for successful handling of masticglues. double roll glue spreader, the fluidity characteristic of normalglues furnishes the means for moving the adhesive through the machineand onto the plies which are being spread. The plies are passed throughthe bite of the applicator rolls which have previously been suppliedwith a roughly regulated amount of adhesive which is transferred fromthe rolls to the upper and lower surfaces of the plies as they passthrough the bite. Both upper and lower rolls form one wall of respectiveupper and lower glue tanks, the tanks in turn being supplied by gravitythrough pipes from a receiving tank or directly from the functioneffectively. The usual glue tanks can, I

of course, be supplied through pipes with glue under pressure from thepositivedlsplacement feeder, but, owing to the lack of self-flow, therevolving glue roll pushes the heavy glue away from its surface, and,unless the parts are considerably modified. influence of gravity isineffective to maintain a sufficient arc of the' roll in contact withthe glue to properly smear its surface. In the case of the lowerspreader roll in all double roll glue spreaders, the glue reservoir hasto be kept well down on the periphery of the roll, since the reservoirtop must be below the bite of the rolls to leave the bite clear andpermit the piles to be fed through the machine. We have found that thisdifliculty can be solved as far as the lower glue tank 45 is concernedwithout changing the location of the glue tank, by enclosing its uppersurface with a cover 46 adjusted to close off the whole top except for'tive displacement pump 21 plus the pumping effect of the downwardrevolving roll 48, as it passes through the gap 41 down into the tank isadequate to generate sufficient pressure in the mass of glue to force itagainst the roll surface with a large arc of contact efiective to keepthe roll surface supplied with glue. In practice, however, we have foundit' difficult to so regulate the feed to the tank as to avoid an excesswhich, of

necessity, escapes through the *gap between the tank cover and thespreading roll. A convenient solution of this overflow difficulty is tosupply one or more overflow outlet conduits or chimneys In the ordinary19, through which excess glue can escape. If

these chimneys are placed'close to the ends of the spreader roll 48clear of the stock passing through thespreader, they may be run up pastthe upper roll 50 so as to provide a supply of glue for the upper gluetank 5!. As will be explained subsequently, the latter does not need tobe enclosed. A further improvement has been to leave the chimney 49 openon the side next to the upward revolving surface of the upper spreadingroll 50, which permits the friction between the heavy glue and theupward revolving upper spreading roll to assist in lifting the glue up,carrying it over and transferring it into the upa per glue hopper 5|.

Since the upper gluetank or hopper is above the bite of the spreadingro1ls,.there is no restriction as to its location on the periphery ofthe roll or as to its capacity. We find that if it is located up high onthe periphery and arranged to allow the roll surface itself to form thegreater portion of the floor or bottom of the tank instead of merelyforming one side-wall as in the prior practice, then a sufllcient weightof glue may be carried in the tank to insure adequate, uniform smearingor coating of the upper roll surface.

' This also provides capacity to accommodate a variable supply and thuseliminates the overflow trouble. This is the only other instance inwhich we utilize gravity in handling mastic glue.

By this method, it becomes possible to adequately supply the surfaces ofthe spreading rolls,

'wood plants to apply the ordinary fluid glues by using metalorsometimes rubber surfaced spreadingrolls provided with reticulatedsurfaces. The simplest and commonest form of surface with metalrolls hasbeen a series of spiral grooves having a pitch or frequency of about tothe inch and separated from each other by a flattopped land or ungroovedportion of roll surface having a width usually about one-quarter thewidth of the groove. Thus, if the pitch is ten to the inch, the groovewill be about eighty thousandths of an inch wide and the land orungrooved portion will be about twenty thousandths wide. The depth andvolume of the groove is then selected to deposit the proper quantity ofglue or spread upon the plies. Owing to the the adhesive, but free fromany excess. To accomplish this result, with a material having the heavyconsistency of mastic glue, we find that two essential modifications ofthe spreader roll functions are necessary. In the first place, the rollbearings, such as are shown at 55, must be heavily loaded by springs 56,so that the spreading can be done under comparatively heavy pressure. Wefind that the pressure necessary for properspreading is about 100 lbs.per linear inch of core'stock width in the bite of the rolls. Thispressure may vary, in some instances, from as low as fifty to as high asone hundred-and fifty pounds, but, in all cases, it is several timesgreater than the corresponding pressure used to spread fiuid glues whichis normally only about ten pounds per linear inch. Moreover, we findthat greatly improved results are obtained if steel rolls, instead ofrubber or rubber covered rolls, are used, since it is necessary tosqueeze the lands of the spreading rolls down through the heavy glueunder this high pressure, so that the glue in the grooved portion maycontact the wood and be transferred to the wood in the desired form of aridge of glue. If these high pressures were used with rubber rolls, thelands and grooves might be deformed to a sufficient degree to preventfluid character of the glue, the linear spread pattern is almostentirely destroyed by self-flow'at the moment when the core stockemerges from the bite of the rolls, but this method gives a roughcontrol of spread which, while objectionably lacking in precision,proves adequate due to -the large volume of fluid glue which is ordi-.narily applied. With the mastic glue, it has'been found that if extremeaccuracy of deposit can be obtained, the volume applied can be reducedabout 50% as compared to the equivalent fluid glue. As described in ourcopending application,

Serial No. 95,460, this accuracy of distribution is obtained by patternspreading the glue in definite ridges separated by areas merely wettedwith proper pattern deposition of the glue.

It is also necessary to subdivide the distribution of glue on thesurface more than with fluid glues. The latter are able to flow outsideways from the areas of excess glue application, so that a pitch often grooves per inch produces a fairly uniform distribution of the glueover the surface of the ply, this distribution mostly occurring byactual sideways flow as the core leaves the bite, of the rolls, but is'further spread out mechanically when the plies are squeezed together,With a the mastic glue which has no self-flow in small masses, thedeposit is left in definite ridges which, in order to produce theultimate desired all over film deposit, must be caused to spread outsideways over the intervening land or unspread surface wholly by thebonding pressure which is subsequently applied to the plies. For thisreason, in order to produce the desired exceptional uniformity ofdeposit which is essential,

since the volume applied is to be reduced about 50%, we find thefrequency of pitch of the grooves in the applicator rolls must beincreased as much as is practical. This distribution by frequency ofpitch has been found quite critical with mastic glues in gluing plywood.A pitchoi about sixteen grooves per inch is desirable, as indicated inFigure 4, but, in some instances, may

be as low as fourteen or as hight as twenty per inch. Above'twenty, ithas not proved possible to deposit enough glue, and below fourteen thespace between theridges is too great for satisfactory final distributionand it is also diflicult to hold the spread down to the proper amount.Of

course, it is understood that the volume deposited by the groove iscontrolled by its cross section which is adjusted as desired to producethe right spread. We have thus found in prectice that neither thepressure nor the grooving of the ordinary spreader rolls used for fluidglues can be employed successfully in spreading mastic glues'and that itis essential to provide a great increase in available spreading pressureanda substantial increase in the frequency of the pitch of the grooving.

By making these modifications with proper equipment and suitablehandling, mastic glue can be spread at very low rates with a degree of4. Assembling the plies tween the amount of spread and the amountofserious difliculty with all fluid glues has been that I this handlingcauses wipes, both due to the pressure of the operator's fingers on thesurface of the core and to wiping action as the core piece its heavyconsistency such handling does not seriously displace it. At most, theridges of the pattern deposit are simply flattened locally, but thelocal quantity of glue remains undisturbed and the handling does notcause any areas of no adhesion or of defective adhesion. This featureforthe first time removes one of the serious defects which haveexistedhitherto in practically all plywood.

Duringassembly, the mastic glue provides another advantage. Owing to itsthick heavy character, it does not act as a lubricant; in fact, therough ridged surface of the deposit has a valuable "non-skid qualitywhich completely prevents the plies sliding around on each other duringthe handling of assembly and loading into the press. This removesanother of the common causes of defective plywood, for with fluid glues,displacement of the relationship between the individual plies is commonand consequent open joints between core stock, overlapped cores andfailure of the panel to trim out to the full size are a frequentoccurrence. With the mastic glue, once the parts are assembled in properrelation to each other, they maintain that relationship so that thenon-skid character of the mastic glue has proved a very valuable featurein practice.

In all gluing practice with aqueous dispersed glues, it is necessary tocontrol the assembly time or interval which elapses between assembly ofthe spread plies and the application ofthe bonding pressure. If theassembly time is too long,

the glue is apt to dry up and produce a weak bond due to insuflicientpenetration, while with fluid glues, the reverse trouble may occur ifthe assembly time is too short, in which case the glue may not havethickened sufllciently from contact with the'porous wood and henceexcessive penetration occurs with the formation of a starved joint. Infir plywood manufacture the usual assembly time tolerance is betweenabout ten and about thirty minutes, but these limits are largely fixedby the specific character of the glue and the wood. It is not,therefore, possible to any marked extent with fluid glues to vary theas'-= vmally very much less than with fluid glues, there is neverthelessa very distinct relationship beassembly time which is permissible, sothat it is possible to economize by adjusting the spread to the assemblytime. Attention is called to the chart, Figure 6, which representsactual experience' with this relationship with a typical low costsoybean mastic glue which has been used extensively. It is noted thatthe practical limits of assembly time tolerance have been found to liebetween about one-half minute and ten minutes and that to produceequivalent bond strength it only requires about fourteen and onethirdpounds of dry glue base per thousand square feet of three ply panelswhen the assembly time is held down to one-half minute, while, when theaverage assembly time is extended to ten minutes, almost twenty-sixpounds of dry glue base are required. In view of this relationship, itis seen that marked economies can be obtained by providing facilitiesand apparatus adapted to reduce the average assembly time and that thequantity of glue spread should be controlled with relation, to theaverage assembly time which will be used in any specific instance.

Control of this relationship is, therefore, a useful feature of ourprocess.

'5. Hot pressing Having controlled both the spread and the assembly timein proper mutual relation, the panels are loaded into the hot press andwe preferably apply the maximum mechanical pressure which the wood willstand without crushing. With Douglas fir this runs from' 200-225 lbs.per square inch. This amount of pressure immediately distributed quicklythickens to form the initial glue bond. With a press plate temperatureof about 230 F. and two three-ply three-tenths inch fir assemblies ineach pressopening, after two and one-half minutes, a large amount ofheat has been stored in the plies and the bond has reached suflicientstrength so that no injury to the bond or separation of the plies ,canoccur upon release of pressure.

- 6. Completing the glue bond When this condition is reached, the pressis opened 'andthe panels are discharged to a close pile, so that themaximum amount of heat is retained within the wood structure; If, inthis manner, the panel is guarded against too rapid-- the mastic glueshave great commercial advantages, which include reduction of glue spreadof up to 50% as compared to equivalent fluid glues, reduction ofobjectionable water injected into the pliesof over 60% with consequentdesirable low moisture content in the plywood, almost entire eliminationof stains due to migration of glue water away from the surface actuallycontacted by the adhesive, reduction in tendency to check due to lowwater content and the elimination of defects and troublesome featureswhich have characterized theuse of fluid glues, such as wipes, skiddingof the plies, etc.

In- Figure 6, we have illustrated, diagrammatically, the preferred stepsin the method of manufacturing plywood in accordance with the presentinvention, and have shown the manner in which the glue and the woodplies are processed, handled or manipulated separately until they reachan assembly station or stations; together withv the manner in which theassemblies, comprising plies and glue, are jointly processed,manipulated and handled until the complete plywood panels are formed.The dry glue ingredients and water are mixed at 60, whereupon the glueflows by .the combined actions of gravity and the mixing blades to areceiving vessel 6|. The glue is then forced by the circulating'bladesin the receiving vessel to the pump 62, from which it is forced to theglue spreading device 63. Face plies from stacks 64, 65 are assembled at66 with core plies which have been fedfrom a stack 61 through thespreader B3.

pressedassemblies are piled in a stack 10 and stored for a suflicienttime to enable the heat in the panels to complete the setting of theglue tdmake a final bond.

The assemblies are subjected to' heat and pressure in a hot press 69,-and the the invention must be considered to cover all vmodificationscoming within the scope of the ing in its floor, a force pump having itsinlet connected to said opening, powermeans for circulating a supply ofsuch glue in said vessel and including means for forcing glue underpressure through said discharge opening into the inlet of the pump,upper and lower glue applicator rolls having grooved surfaces, conduitmeans for delivering glue from the outlet of the pump directly to thelower of said rolls only and for maintaining a body of glue in contactwith the surface of that roll under pressure, and additional conduitmeans for conducting glue from said body of glue upwardly into contactwith the surface of the upper roll. i

2. An apparatus for adhesively coating core plies with a semi-fluid glueof such a viscosity as to be incapable of self-flow when applied to theplies in a pattern spread comprising excess glue areas and intermediateareas merely wetted with adhesive, said apparatus comprising a pair ofoppositely rotating, horizontally disposed upper and lower glueapplicator rolls having grooved surfaces, means on the downwardlymoving, discharge side of the lower roll defining a chamber having asubstantially closed top and an open side facing said roll, means fordeliver-- ing such heavy glue under pressure from a source of supply tosaid chamber, conduit means extending upwardly from said chamber andhaving an open side adjacent the upwardly moving,

discharge side of the upper roll, whereby glue under pressureflowsupwardly into contact with the upwardly moving face of the upper rolland Although the invention has been described in considerableparticularity, it must be understood that the foregoing descriptionandthe accompanying drawings are illustrative only and that "is carriedupwardly therewith, andmeans defining a glue trough on the downwardlymoving, inlet side of the upper roll, said means having an open side orbottom facing said upper roll..

THEODORE WILLIAMS m cs nanny GALBEB.

